In the prior art there are disclosed many types of devices utilized for forming a straight tube into a serpentine configuration for use, for example, as a refrigerator coil. U.S. Pat. No. 4,753,098 issued June 28, 1988 and assigned to the assignee of the present application discloses a tube forming apparatus utilizing bending rollers which are interconnected by lazy tong linkages so that each set of a pair of bending rollers may be simultaneously brought together while one set of rollers is separated from the other set of rollers. While the method and apparatus disclosed in U.S. Pat. No. 4,753,098 has been effective in producing refrigerator coils, it has been found that the apparatus disclosed in the aforesaid patent could not provide sufficient tension to form small radius bends in the tube.
There are other prior art references which disclose various types of mechanisms for bending tubes. Japanese patent 63-149022 issued June 21, 1988 discloses sets of bend forming elements slidably mounted on guide rails wherein the guide rails are moved apart as the sets of bend forming elements are moved together so as to form a tube into a serpentine configuration. The Katogir U.S. Pat. No. 3,722,254 issued Mar. 27, 1973 discloses a tube bending apparatus including a series of material forming heads which are movable relative to each other and movable from retracted to extended positions. While the aforesaid patents disclose equipments capable of forming tubes into a serpentine configuration, the prior art does not provide the particular combination of elements disclosed in the present invention which operates to produce small radius bends in tubes.